We will examine age-related auditory loss in AU/Ss, C57BR/cdJ, LP/J, A/J, SJL/J and AKR/J mice, utilizing the auditory nerve and brainstem evoked auditory potential technique, hair cell counts and spiral ganglion cell counts. Young, middle age, and old mice of the CBA/J, AU/SsJ, SJL/J, AKR/J strains will be subjected to varying doses of ototoxic aminoglycosidic antibiotics or high intensity noise, and the interaction of genotype with age and agent will be investigated. We have recently demonstrated that the late-middle aged CBA/J mouse i more susceptible to kanamycin than is the young CBA/J mouse. We will extend this into old age, and examine the other genotypes for the same effect. If one or more older genotype is not more susceptible to ototoxic drugs, or the noise trauma, we will attempt to find out why. We will continue the Golgi study on the aging mouse auditory cortex, attempting to determine a more precise relationship between synaptic loss, aging per se, and aging with associated peripheral hearing loss. With a larger number of subjects, we should also be able to determine whether reclamation occurs in the auditory cortex of the deaf, aging mouse.